Method for treating bagasse and similar fibrous products for the production of pulp and the extraction of cellulose



Patented July 7, 1931 UNITED STATES PATENT; oi -fFlcs RAYMOND CHARLES MOQ'UISTON, OF NEWTON, AND HARRY VON LOESECKE OI ARLINGTON, MASSACHUSETTS, ASSIGNORS TO UNITED FRUIT COMPANY, OF BOSTON, MASSACHUSETTS, CORPORATION OF NEW JERSEY I FOR TREATING- BAGASSE AN SIMILAR FIIBROUS PEODUOTS 'IOB,v THE PRODUCTION OF PULP AND THE EXTRACTION OF CELLULOSE No Drawing.

Our invention relates to a process for treating the bagasse of sugar cane, bamboo, banana stalks, corn stalks and other similar fibres in order to produce therefrom'pulp available for use in pape'rmanufacture, and further provides for the treatment of such pulp to extract therefrom substantiall pure cellulose adapted for use in the manu acture of ra on and in other industries.

It is further an important purpose of our invention to provide a process inthe practice of which it is possible to dispense largely with the use of fresh water in the treatment of the fibres to produce the desired ma- 1 terial, this being desirable for the reason that in many of the regions where supplies of bagasse are available fresh water supplies are limited but sea Water is readily available.

By our process We are enabled to dispense largely wth the use .of fresh water and to use sea water instead. Inits broader. aspects, however, o-ur invention is not limited to the use of sea water.

In bagasse, corn stalks and similar prod- 'ucts pithy material is closely associated with the fibres. The first step in our process consists in the separation, mechanically, of the pith from the fibre's. This may be accomplished by various mechanical means, but we prefer to subject the bagasse or other fibre to the actionof a swing hammer mill because the crushin action ofsuch a mill tends to open up the bres and to prepare them better for the action of salt water than'is accomplished by other means After this mechanical treatment, the pith, dust and fines or very I short fibres are separated fro-mthe longer fibres by an air-blast is an air separator.

We no take the longer fibres,'free from the pithy aterial, dust and fines, and place them in a. digester of any suitable type, which is preferably provided with a suitable means for circulatlng the cooking liquor during di gestion. We then introduce a cookin liquor consisting of a solution of sodium hy roxide with or without 'soda ash in sea water. We prefer to use for every 100 pounds of dry bre about 100 gallons of water, sodium hydroxide equal to' 1.5-18% by weight 'of the dry fibre, and soda ash equal to' 5-8.% by

' tens the bleaching operation.

. is preferably maintained at a temperature of Application filed April 30,1930. Serial No. 448,780.

weight of thanlry fibre. We also introduce into the cooking liquor 24% of a soapy material, preferably an alkali cellulose in saponified fatty acids. Sodium bisulphite may, if desired, be added to the extent of 4-8 based on the weight'of the fibre.

We find that by cooking the fibres in this solution at pressures ranging from 25-30 pounds per square inch gauge for from 2-5 hours, we obtain a pulp of suitable quality for paper manufacture; These pressures are notably low as compared with those employed in other digestion processes with which we are acquainted. a

After cooking, the cooked fibres are washed, preferably with hot sea, water, and then subjected to a beating process. This may be accomplished in an ordinary beater engine but we prefer to employ, instead, the form of apparatus disclosed in the co-pending ap lication of Raymond Charles McQuiston, erial No. 448,461, consisting essentially of a'form of gear pum through which the pulp mixture is circu ated, which accomplishes more.

simply and cheaply the results usually accomplished by a beater and jordan treatment. The beaten fibres are now in condition to be utilized for the manufacture of kraft stock,

cardboard and pressed and molded insulating materials, artificial lumber, etc. 1

If a higher grade pulp is desired for use in the manufacture. of better grades of paper or for the extraction of pure cellulose, we new subject the pulp toa bleaching, which is preferably accomplished by a solution of calcium hypochlorite in sea water. Other bleaching solutions may be used, if desired. It is our opinion, however, that a salt water solution 7 of calcium hypochlorite considerably has- 90 We prefer to use 25-30 gallons of 3.0 to 5.0 Baum calcium hypochlorite solution for every 100 pounds of wet pulp. The bleached solution 05 from to F. and the bleaching continued for from one-half to one hour. Duringthe last ten minutes ofbleaching we prefer to add to the bleaching solution about one pint 50% acetic acid or smaller amounts of 100 sulphuric or hydrochloric or similar acids for every 100 pounds of wet pulp. v

The bleached fibres are now thoroughly rinsed, preferably'first with sea water, and finally with fresh water, and are then ready for felting into dried pulp or for manufacturing directly into all grades of paper. The pulp obtained at this stage is snow white.

For the production of alpha-cellulose we now take the bleached pulp produced as aforesaid and treat it with a 12-18% solution of caustic soda in sea water maintained at 7080 F..for 40-60 minutes, depending upon the degree of purity desired. We have found that a 5% solution of sodium hydroxide will yield a product containing about 84% of alpha-cellulose, while a 15% solution of sodium hydroxide will yield a product containing about 93% of alpha-cellulose.

The product is now washed in cold sea water and then suspended in a 1-2% cold fresh water solution of oxalic or acetic acid for 3(l-40 minutes, after which it is again ess is equally applicable to other fibrous materials of similar characteristics such as corn stalks, bamboo, banana stalks, etc. and it will be understood that such materials are included within the general sco e of the word bagasse as used in the su -joined claims. It will also be understood that where in the subjoined claims we refer .to the extraction of cellulose, we mean to include not only the extraction of pure cellulose, but of semi-cellulosic or cellulosic materials such as pulp suit: able for use in the manufacture of paper and paper products.

We claim as our invention:

arating the long fibres from the fines and pith, and then treating the long fibers with a solution of sodium hydroxide in sea water.

5. The method of bleaching semi-cellulosic I sists in subjectin the fibres to treatment with a solution of s ium hydroxide at substantially atmospheric temperatures.

8. The method of extracting alpha-cellulose from bagasse which consists in mechanically separating the long fibres from the pith and fines, treating the long fibres with a solution of sodium hydroxide in sea water,

washing and bleaching the treated fibres, and J then subjecting the washed and bleached fibres to further treatment in a solution of sodium hydroxide and sea water.

' RAYMOND CHARLES McQUISTON.

HARRY von LOESECKE.

1. The method of extracting cellulose from with a solution of sodium hydroxide in sea water.

2. The method of extracting cellulose from bagasse which consists in treating the same with a solution of sodium hydroxide in sea water at relatively low pressures of the orderof 25-30 pounds per square inch.

g 3. The method of extracting cellulose from bagasse which consists in treating the same with a solution of sodium hydroxide in the presence of an alkali cellulose in saponified fatty acids. f

4. The method of extracting cellulose from bagasse which'consists in first; subjecting the bagasse to treatment in a hammer mill, sep- 

